Aeroponic plant growth is plant husbandry without soil and without roots continually immersed in water, as is the case normally in hydroponics. Most aeroponic systems, while not employing soil, do require a medium for roots to gather around. Clay pebbles are often used. In aeroponic systems roots can be watered by intervals of periodically resting in water followed by intervals of being only in air. Alternatively, roots in air can be sprayed with water. Aeroponic techniques have long been proven as a viable and efficient method of plant growth but have not found widespread acceptance for several reasons.